System for automatic sample analysis and a method for producing the system including a cleaning unit for a movable optical head

ABSTRACT

A system for on line analysis of material samples in accordance with the invention includes a grinding mill for comminuting sample material to output comminuted sample material; an analyzer unit for performing the on line analysis of the outputted comminuted sample material and having a housing holding an optical system having a front glass with the optical system performing the on line analysis of the outputted comminuted sample material, and a receiving chamber for receiving the outputted comminuted sample material from the grinding mill; and a mechanism for moving the housing relative to the receiving chamber between a first position at which the front glass closes a wall opening into the receiving chamber and a second position at which the front glass is cleaned by a cleaning mechanism.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sampling and analysing equipment foruse in systems for receiving raw materials, in particular biologicalmaterials for delivery in a mixed or a processed condition in smallerportions or delivering materials in mixed or processing condition.

2. Description of the Prior Art

In WO/89/11090 is already described the advantages of using an automaticsampling equipment already described, from which samples of newlyreceived materials can be rapidly transferred to a central analysingstation, wherein the single samples are quickly analysed, thus enablinga quality determination of the new materials as a basis for a correctaccounting in view of the qualities as well as for a rapid adjustment ofprocessing or mixing conditions, should the new materials exhibitchanged properties, regarding their content of fat, water or protein. Atypical relevant application in preparation of fodder mixtures forlivestock.

The equipment disclosed in the aforementioned WO publication isrelatively expensive, and it is well applicable in large applications.In practice it is not suited for use in smaller applications, where itis an economical burden to arrange for automatic samplers and apneumatic conveyor system between the sampling system and the analysingequipment. At least to a certain extent it is fully acceptable tomanually carry the samples to the analysing equipment with the latterbeing simplified.

SUMMARY OF THE INVENTION

In connection with the invention it has been recognized that in fact itis possible to modify existing laboratory equipment to make it usablefor automatic, successive samples handling and analysing, such that witha relatively modest investment it is still possible to achieve anoticeable increase of the analysing capacity with a minimum oflabouring.

Two laboratory units are usable for this purpose, vis. an analyzer basedon the so-called NIR principle and a grinding mill for comminuting thematerial to be analysed. In their known standard designs both of theseunits require a careful manual cleaning prior to each new operation.With the invention it is important that the required cleaning can takeplace automatically immediately after each operation such that theequipment will rapidly be ready for handling a new material samplewithout the new material sample being unduly contaminated by remnants ofthe previously handled sample material.

The commonly used grinding mills are unfit for cleaning in a sample andautomatic manner. These mills have a knife rotor rotating inside asurrounding screen, outside of which there is an annular bowl forreceiving the comminuted material. This bowl unit is made with rathersharp inner corners. Even if it is reasonably easy to clean manually, itwill be difficult to clean in any simple, automatic way. According tothe invention such a mill may be modified to form an automaticallyeasily sealable unit, viz. by replacing the bowl unit with rigid insertparts, which, together define a receiver chamber having an evenly curvedouter wall which is much easier to clean than the conventional bowlswith sharp edges with the use of air nozzles. The insert parts may forma tangential outlet, thus enabling the mill to work on-line.

The laboratory units for NIR analysing comprise a cabinet having anoptical head against which can be placed a cuvette holding a few gramsof the material that is to be analysed upon being comminuted. After eachoperation the cuvette should be cleaned with spirits with all handlingbeing performed manually. According to the invention it is possible tomodify these units to an automatic on-line operation. It is an importantaspect of the invention that the units are modified standard units ownedby users desiring to change into automatic sample handling andanalyzing. The reason for this is that such a user will already havespent a considerable amount of capital for achieving a good calibrationof the measuring apparatus which requires a high number of expensivechemical analyzes. The detailed calibration base will be inseparablyassociated with the individual apparatus. For this reason it is highlyadvantageous that it is the already existing apparatus which is beingmodified. It has been found to be permissible to move the associatedoptical head to a different apparatus unit in order to make possible anautomatic sample handler.

Similar but less stringent circumstances apply to the grinding mill. Ifstrictly required a mill may be replaced by another mill, but preferableonly of the same brand and type, because the accuracy of the resultinganalysis is closely dependent upon the samples being prepared in thesame manner as when the calibrations were made.

With the use of the relatively inexpensive laboratory mills it ispossible to handle materials with a coarseness up to about pea size.With the invention it has been found possible to work with sampleportions considerably smaller than the approximately four liters asspecified in the WO/89/11090, viz. 200-300 ml. The samples may besupplied from external samplers or sample terminals via pneumaticconveying. Owing to their small volume and the limited capacity of thesystem it will normally be acceptable to just scrap the samples withoutreturning them.

If with a given user still coarser materials are to be handled, it willbe required to pre-prepare these materials by comminution to thefineness required for an effective milling in the aforementionedgrinding mill. This can be arranged in the conventional manual mannerwith the use of a suitable chopping machine. However, according to theinvention, it will also be possible to arrange this chapping unit as anon-line module in operative connection with the basic system of the milland the analyzer. As in WO/89/11090, this module may be connected withvarious automatic samplers and sample terminals. It is preferred to workwith sample portions of the magnitude of four liters. The module maycomprise a divider that sends a smaller sample, e.g. 250 ml, to the milland analyzer, while the major part of the sample, 3.75 1, may bereturned or scrapped.

The basic system may be supplemented by a receiver unit for the analysedsamples. The receiver unit may easily be adapted so as to distinguishbetween sample refuse to be scrapped and sample portions which, from ananalyzing standpoint, are more interesting, such that they should becollected for further reference analysis.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, which is defined in more detail in the claims, will nowbe further explained with reference to the drawing, in which:

FIG. 1 is a schematic diagram of a system according to the invention;

FIG. 2 is a sectional view of a grinding mill therein;

FIG. 3 is a perspective view of an associated NIR analyzer;

FIGS. 4-6 are other views thereof; and

FIG. 7 is a perspective view of a sample discharge station in thesystem.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The system shown in FIG. 1 is basically divided in A, B, C, and D.Section A is the basic module in the system is which the user switchesfrom a manual laboratory handling of arriving samples to a fullyautomatic handling thereof with a maintained calibration of a previouslyused analysing unit based on the NIR principle or principles comparablethereto.

An already existing NIR analyzer 2 is located in Section A with itsoptical head 4 taken out and mounted in a cabinet 6, which is movablerelative to a test chamber 8 as described below. This chamber receivescomminuted sample material from a mill 10 with the sample materialpassing through a cyclone 12 and then to a homogenizer 14. After theanalysis the samples are conveyed through a bottom outlet 16 of thechamber 8, optionally to the module D, which is described in more detailbelow.

The mill 10 can be supplied with test material from receiver terminal18, from which the material is supplied through a conduit 20, driven bythe suction of a suction fan 22, which, in Section A, draws conveyingair from the mill 10 to the cyclone 12. However, the supply conduit 20may also be connected to external samplers or terminals 24 in section Cas well as to a discharge conduit 26 from section B.

If applicable, the mill 10 may be a previously used laboratory mill,which is then only modified according to the invention as illustrated inFIG. 2. Such a mill will typically have a lower motor housing 28 with acentral top mounting 30 having along its periphery an vertical standingannular screen 32 having an inner side of which is swept by a kniferotor 34. A tray member 36 surrounds the screen 32 and is closable, inthe original design, by a cover not shown. According to the invention,the tray 36 is replaced or filled out with an annular body 38, shown inhatching, which is made with a tangential outlet 40 and crosssectionally shaped with an evenly curved inner wall 42. This annularbody is at plural places provided with compressed air nozzles 44enabling an effective cleaning of the chamber after each passage of asample.

A supplied sample after a remainder is blown off is conveyed from themill 10 suitably comminuted, via the cyclone 12, to the homogenizer 14.The homogenizer 14 serves the same purpose as the unit designated 5 inFIG. 4 of WO89/09388, which homogenizes the received material therein.In the present invention, however, a different unit is used, viz. anapparatus working according to a known principle as a real mixing unitwhich is used only for self-mixing of the successively supplied samples.It has been found that it is then possible to avoid the use of thespecial measuring homogenizer which according to the WO publication isprovided inside the test chamber as identified by reference numerals 36,38.

Because the mixing unit is of a known type, it is only brieflydescribed. According to FIG. 4 it comprises a horizontal cylindricalhousing 50 accommodating a rotor 52, which for an outer worm winding 54with a conveying pitch in one direction and an inner worm winding with apitch in the opposite axial direction. It is known that more materialsfed to the top of the rotor housing 50 can be effectively mixed.According to the invention a very effective sample homogenizing of onlya single material can be achieved. In connection with the invention, theknown mixing principle will provide not only for a good homogenizing ofthe received single material but also for a relatively small contactarea between the material and the respective working units, such thatthe risk of sample contamination from previous samples can be kept aslow as possible.

From the fine homogenizer 14 the discharge material is fed down into theanalysing unit 6, 8, which, in principle, may be designed just asdisclosed in the WO publication. It should be mentioned, however, thatin connection with the invention it has been found possible to simplifyalso this part of the entire system, so as to obviate the use of acomplicated and operatively expensive feeding of a separation filmbetween the sensor head of the analyzer and the sample material. This isachieved by effecting a cleaning of the sensor head by blowing, wipingor ionizing of the head, which in a NIR based system will exhibit acover disk of quartz glass. It is sufficient to clean the outside ofthis disk between the analyzing of the successive sample portions. Awiping can be effected with a moving cleaning web attached to a rollerwhich is moved along the outside of the quartz glass, such that thewiping will take place in a progressive and concentrated manner

As mentioned, but not shown in more detail, there are mounted, at allqualified places in the system, air nozzles for interior cleaning andflushing of the different units.

The numeral 11 denotes a connection for by-passing the mill forsupplying products not requiring to be milled.

With the invention it is a basic consideration that the use of themixing unit 14 as shown in FIGS. 1 and 4, downstream of the cyclone 12,provides a high degree of homogenization of the treated samples to beachieved, such that each of the samples, when deposited into theunderlying test chamber 8, will remain sufficiently homogenous for theanalysing measurements to be correct. For the same reason, however, itis preferred that the measuring window in the test chamber be relativelylarge, viz. so much larger than the required measuring area that thereis area sufficient for making separate tests on two or more differentareas of the window, e.g. as illustrated in FIG. 6. It is possible toeffect a successive shift of the sensor head, designated 60, relative tothe test chamber. If in this way, e.g. four measurements are made atdifferent places of one single sample, a representative average resultcan be obtained. The associated data processor may trigger an alarm, ifthe difference between the single measuring results is unacceptablyhigh, indicating that the homogenization is not good enough. If so, itis possible to repeat the test with a new sample of the same material,or to take out the sample for chemical analysis.

When the test window, 62 is thus required to be relatively large, thetest chamber will have to be correspondingly high and wide. With sampleportions of the magnitude 250 ml, the chamber then has to be so thin,(See FIGS. 3 and 4), that it will be thinner than the outlet openingbeneath the homogenizer 14. IN order to counteract a separation in thesample material it is desirable that the entire sample be deposited atone time into the test chamber 8. This may be accomplished by a suddenretraction of a valve plate 64 at the outlet from the homogenizer 14.Due to the reduced thickness of the chamber 8, there has to be a certainnarrowing 66 downwardly. It will be noted that this narrowing is locatedabove the chamber side opposite the test window 62. The reason for thispositioning is that the depositing of the material next to this windowshould preferably be as direct and undisturbed as possible.

In the analyzer equipment as shown in FIGS. 3-6, the measuring window 62is a regular hole in the wall of the test chamber 8, while theassociated window glass, designated 68, is mounted on the apparatuscabinet 6 containing the measuring optics 4 for effecting the analyses.Inside this unit the optical head 4 is mounted in such a manner that itcan be moved between the four different positions shown in FIG. 6. Inaddition, the whole cabinet 6 is mounted on a movable support 72 whichis displaceable by means of a cylinder 70, while the support 72 istransversely displaceable by means of a cylinder 74. It is possible tomove the cabinet 6 in FIG. 3 a distance to the left and thereafterforwardly against the test chamber, until the window 68 seals over thehole in the wall of the test chamber, which can thereafter receive asample to be analysed.

Upon the depositing of the prepared sample portion from the chamber 14to the test chamber 8 a projection of a piston plate 78 from the rearside of the chamber 8 is arranged by means of a cylinder 76, where thisplate is housed in a housing portion 80, such that the sample materialadjacent the window 68 is compacted against this window. During theanalysing process the sample material should be kept absolutelyundisturbed. It is preferred, therefore, to stop the piston plate 78firmly in its projecting position which is accomplished by means of acrosswise arranged pressure cylinder 82 on the piston cylinder 76.

When the analysis has been made, i.e. when measurements have been madewith the measuring head in the respective four positions according toFIG. 6, the piston plate 78 is retracted into the housing part 80, andthe discharge pipe 16 is connected with a suction fan for sucking outthe sample with preferably the suction fan 84 being located in thedischarge section D. The fan may be an ordinary vacuum cleaner. The testchamber will be emptied from below.

After the emptying of the test chamber an important method step isperformed, which is not further illustrated, viz. a blowing in ofcompressed air through air nozzles in or against strategic places in theentire system 14, 8, so as to achieve an effective cleaning of thesurfaces which have been in contact with the test material. It should bestressed that in addition to stationary nozzles one or more nozzles maybe mounted in connection with the driving shaft of the rotor in thehomogenizer 14. Another measure will be to arrange for an extra powerfulblast of air sweeping of the window glass 68, as the material beingpositively pressed thereagainst. The same applies to the piston plate78. However, for NIR analyses, this will be less critical, because smallremnants on this plate will not effectively contaminate the subsequentsample. However, if the analysis is based on a view of illuminationthrough the test chamber, i.e. where also the said plate is translucent,this plate should of course also be effectively cleaned.

After this cleaning it could be possible to continue with the nextsample, given that a relevant accuracy standard for the analysis of thenext sample can be observed. However, this will be possible onlyexceptionally, as it will normally be required to ensure an extra goodcleaning of the window glass 68. It is primarily for this reason thatthe analyzer 6 is mounted in a movable manner so that it will then bepossible to expose the window for an external and more effectivecleaning thereof.

For achieving this cleaning there is mounted, next to the test chamber8, as separate, box-shaped unit 86, (See particularly FIGS. 4 and 5),having at its front side a projecting roller 88 acting as a sprocketroller for a cleaning web 90, which is reeled off from a supply reel 92and is reeled onto a reel driven by a stepmotor 96 as illustrated inFIG. 4. The cleaning web 90 may be a non-expensive, impregnated paper ortextile web, which, for each operation, will only have to be advanced asfar or as to expose a clean web portion on the roller 88.

With the said movability of the analyzer 6 it will be possible to movethis unit such that its window member 68 is brought to scrape over theroller 88, whereby remaining sample resting thereon will be cleaned ofeffectively. Normally, it will not be required to advance the cleaningweb during this operation, as the web will be smudged very little duringthis operation. Some trace of impregnation agent may be left on thewindow. If this affects the result of the next analysis, the window willhave to be dried or wiped before it is brought to a renewed operativeconnection with the window hole 62. This is possible by moving thewindow past special air nozzles or past a wiping unit corresponding tothe unit 86.

In the system is also arranged a special measuring plate 98, (See FIGS.4 and 5), contacts the window member 68 on the analyzer unit 6 may bebrought to contact by a suitable moving of this unit. The plate 98 is aceramic which, when subjected to an analysing measurement, providesknown reference results to permit checking of whether the cleaning andthe operation of the measuring equipment is correct.

IN the discharge section D the sample material is sucked to a cyclone100, from which it is be delivered to cups 108 on a conveyor 110. SeeFIG. 7. Alternatively, by means of a switch over valve 102 the materialmay be fed to a cyclone 104, from which it is discharged to be scrapped.A controller computer may control an emptying into a cup 108 when ananalysis result is found so peculiar that a subsequent laboratoryanalysis of the sample is referred. Suitably, therefore, this part ofthe system may be mounted directly at or in a laboratory, possibly at adistance from the cyclone 104.

The module B of FIG. 1, is a coarse milling unit containing a knife mill112 and a suction fan 114 for sucking the sample material to this milland further sucking the product to a cyclone 116, which, via a dischargeunit 118, is delivered to a divider 120. It is preferred to feed themodule B with sample portions of approximately 4 1, and the divider 120should deliver approximately 250 ml to the module A through the conduit26, i.e. for each sample the divider delivers 3.75 1 through a dischargeconduit 112, from which the material may optionally be returned to therelevant source, e.g. a silo.

A suction conduit 124 to the mill 112 in module B may be connected witha local sample receiver 126. It is also a possibility that the conduitcan be connected with various automatic samplers or external sampleterminals in the system designated C.

In addition to the cleaning by means of compressed air at strategicplaces in the system, in order to keep the system clean, the variousparts thereof, particularly the mill 10 and the cyclone 12, should bekept warm to counteract condensation of sample material on the innersides.

We claim:
 1. A system for on line analysis of material samplescomprising:a grinding mill for comminuting sample material to outputcomminuted sample material; an analyzer unit for performing the on lineanalysis of the outputted comminuted sample material and having ahousing holding an optical system having a front glass with the opticalsystem performing the on line analysis of the outputted comminutedsample material and a receiving chamber for receiving the outputtedcomminuted sample material from the grinding mill; and a mechanism formoving the housing relative to the receiving chamber between a firstposition at which the front glass closes a wall opening into thereceiving chamber and a second position at which the front glass iscleaned by a cleaning mechanism.
 2. A system in accordance with claim 1wherein the cleaning mechanism comprises:a cleaning housing which ismoveable relative to the housing holding the optical system; animpregnating cleaning web projecting from the cleaning housing forcleaning the front glass of the optical system as the cleaning housingis moved relative to the housing holding the optical system between thefirst and second positions; and a driving mechanism for advancing theweb.
 3. A system in accordance with claim 1 wherein:the optical systemis disposed behind the front glass in the housing and has a plurality ofoperative positions with the optical system being shifted between theoperative positions to analyze at least one sample.
 4. A system inaccordance with claim 1 wherein:the receiving chamber receiving samplesof the outputted comminuted sample material having a volume between 200to 500 ml.
 5. A system in accordance with claim 1 further comprising:ahomogenization mixer disposed above the receiving chamber and coupled tothe mill for mixing the outputted comminuted sample material andsupplying mixed outputted comminuted sample material to the receivingchamber.
 6. A system in accordance with claim 5 wherein the mixercomprises:a double screw cylindrical mixer.
 7. A system in accordancewith claim 1 wherein the mill comprises:a laboratory mill having ascreen, an insert portion, disposed adjacent the screen, defining anannular channel between the screen and the insert portion and having anouter rounded wall and a tangential outlet; and inlets within the insertportion for receiving compressed air.
 8. A system in accordance withclaim 7 further comprising:a heater within the insert portion.
 9. Asystem in accordance with claim 1 further comprising:a plurality ofmodular units, one of the modular units containing the analyzer unit andanother modular unit containing another grinding mill for processinglarger volume samples than samples processed by the grinding mill forcomminuting sample material; and the another modular unit furthercomprising a divider for separating a portion of the comminuted samplematerial and discharging the separated portion to the one modular unitcontaining the analyzer unit.
 10. A system in accordance with claim 9wherein:the portion ranges from between 1/10 to 1/25 of a samplematerial contained within the another mill.
 11. A system in accordancewith claim 9 further comprising:a plurality of samplers coupled to themodular units with the samplers delivering samples to the mills with thesamplers delivering samples of a smaller volume to the modular unitcontaining the grinding mill and of a larger volume to the anothergrinding mill.
 12. A system in accordance with claim 10 furthercomprising:a plurality of samplers coupled to the modular units with thesamplers delivering samples to the mills with the samplers deliveringsamples of a smaller volume to the modular unit containing the grindingmill and of a larger volume to the another grinding mill.
 13. A systemin accordance with claim 1 further comprising:a discharge unit connectedto the analyzing unit to deliver portions of analyzed comminuted samplematerial selectively to a scrap container or to at least one additionalcontainer for collecting the analyzed comminuted sample material forfurther analysis.
 14. A method for on-line analysis of material sampleswith a system having a grinding mill for comminuting sample materialsamples to output comminuted material samples, an analyzer unit forperforming the on-line analysis of the outputted comminuted materialsamples and having a housing holding an optical system including anoptical head and a front glass with the optical system performing theon-line analysis of the outputted comminuted material samples and areceiving chamber for receiving the outputted comminuted materialsamples from the grinding mill, and a mechanism for moving the housingrelative to the receiving chamber between a first position at which thefront glass closes a wall opening into the receiving chamber and asecond position at which the front glass is cleaned by a cleaningmechanism comprising:modifying an existing laboratory equipment byremoving the optical head from the existing laboratory equipment andmounting the optical head in the housing in operative connection withthe receiving chamber while maintaining an electrical connection betweenthe optical head and the analyzer unit and an original calibration ofthe analyzer; using the grinding mill to output a comminuted materialsample; providing the comminuted material sample to the receivingchamber and performing tests on the comminuted material sample with theoptical head in the receiving chamber using the original calibration;and moving the housing between the first and the second position aftereach analysis operation.
 15. A method according to claim 14, wherein:theexisting laboratory equipment is modified in that an existing grindingmill therein having a circular screen is used for maintaining theoriginal calibration and is modified to have an insert portion disposedadjacent the screen and an annular channel between the screen and theinsert portion and having an outer rounded wall and a tangential outletas well as inlets for receiving compressed air for cleaning purposes andis used as the grinding mill to output the comminuted material sample.16. A method for on-line analysis of material samples with a systemhaving a grinding mill for comminuting sample material samples to outputcomminuted material samples, an analyzer unit for performing the on-lineanalysis of the outputted comminuted material samples and having ahousing holding an optical system including an optical head and a frontglass with the optical system performing the on-line analysis of theoutputted comminuted material samples and a receiving chamber forreceiving the outputted comminuted material samples from the grindingmill, and a mechanism for moving the housing relative to the receivingchamber from and to a first position at which the front glass closes awall opening into the receiving chamber, comprising:performing ananalysis of a material sample with the housing in the first position;subsequently moving the housing into a second position of which thefront glass is cleaned by a cleaning mechanism; and moving the housingwith the cleaned front glass back to the first position preparatory to asubsequent analysis operation of a new material sample.